cargo-lints are lints emitted by Cargo itself, rather than by rustc or Clippy. They inspect your package/workspace metadata and dependency setup—for example, unknown Cargo lint names, unused dependencies, naming mistakes, or a workspace lint configuration that was not actually inherited.

The configuration lives in Cargo.toml:

[workspace.lints.cargo]
unknown_lints = "deny"
unused_dependencies = "warn"

# In each workspace member:
[lints]
workspace = true

That gives a workspace one place to enforce Cargo-level policy, and lets CI catch manifest mistakes without a separate third-party checker. It does not replace rustc/Clippy lints for source code. The feature is currently nightly/unstable; this stabilization PR is what I was referring to. See the Cargo lint reference.